When driving vehicles through wooded or rough country, the difficulties encountered in advancing the vehicle and the damage caused to the ground when driving create serious problems. Also, when advancing logs or three trunks in log-handling machines, it is difficult to effectively advance the logs without damaging the same.
The abovementioned problems can be generalised by saying that it is difficult to create movement between two mutually contacting bodies when the body contacting the driving means by which the movement is to be effected has a shape which does not favour said movement, and to move said bodies without causing damage thereto.
There are today certain known principles for creating movement between mutually contacting bodies. The principle most applied is the rolling principle. In this respect, many different apparatus are available which are equipped with wheels or belts. Movement between mutually contacting bodies can also be caused by means of walking. There are examples of mechanically driven apparatus which execute walking-like movements, and certain apparatus comprising inflatable hoses or cushions in which different forms of walking movements are achieved by inflating the hoses or cushions in accordance with different predetermined inflation patterns.
In order for apparatus which apply the rolling principle, and mechanical walking apparatus to successfully negotiate obstacles, it is necessary to make them both complicated and bulky. Such apparatus often operate with relatively small contact surfaces, and hence the contact pressure is high. Attempts to increase the contact surfaces, thereby to reduce the contact pressure, often results in large, bulky apparatus. Apparatus which use hoses or cushions of different kinds to obtain a walking-like movement have a very low advancing speed.